In evaluating a subterranean formation, a downhole tool such as a formation tester may be lowered into a wellbore or borehole penetrating the formation and the tool may be used to measure one or more characteristics or parameters of the formation. Acoustic testing is one particularly useful manner of measuring formation parameters such as formation slownesses, which may be used to identify a formation of interest and evaluate the best manner in which to produce hydrocarbon fluids from the formation of interest.
A formation tester or formation testing tool may include an acoustic transmitter and an array of acoustic receivers distributed along a body of the tool. The transmitter may emit acoustic signals or waves, which then travel through the formation and may be received by the acoustic receivers. The times at which the acoustic receivers detect the emitted acoustic waves vary based on, among other things, the distances or spacing between the receivers and the slownesses of the materials through which the acoustic waves travel to reach the receivers. As a result, in general, an analysis of the manner in which acoustic signals are received by an acoustic receiver array on a downhole tool can yield information about the properties (e.g., slownesses) of formation(s) adjacent to a borehole.
However, processing the acoustic signal information or data generated as a result of the acoustic signals or waves received by the acoustic receivers can present certain difficulties. For example, because of the various paths via which acoustic waves may reach the receivers, waves traveling via different paths and/or through different materials may nevertheless overlap in time and/or frequency when detected by the receivers. As a result, analyzing a particular signal of interest and/or removing or extracting a signal of interest from the acoustic data may be very difficult.